This depends on what time of year the logs were cut (which will determine the amount of moisture in the logs) — if the logs were properly seasoned — if the notches are done correctly (so there is uniform weight distribution) — the type of material used — the size of the logs — the height of the log walls — the weight of the roof — the type of log home involved (saddle-notch, Scandinavian chinkless, butt-and-pass, etc).
In other words, this question is not “nearly” complete enough to answer in a meaningful way.
However (here’s the big secret) the method that we primarily recommend to students is not affected by settling at all. So when you cut a window opening you do not need to cut extra space for settling. We know this is hard for students to believe, but it is true. The kit manufacturers don’t want you to know about this method because it would eliminate their business.
One of our students was so confident in our non-settling log home construction method, that he put a roof system on his home that weighs over 25 tons! His roof system consists of concrete tiles, big gluelam rafters, a large ridge log, as well as a 2×6 tongue and groove sub-roof. It all equals a giant amount of weight, way more than is normally put onto the walls of a log home.
His home has experienced zero settling since it was built. even though it has more than the weight of 20 full size Ford F-150s on top of the walls.
You can see this home in our gallery of student built log homes, it’s the one built by retired Navy Chaplain Fred Renfroe.